Compensation For Near-field Aperture Antenna Measurement

Antenna measurement is one of the important projects along with antenna engineering developed. Now the analysis and design of the new high-powered antenna are always with advanced measurement technology and equipments. Near-field measurement has the advantages of high accuracy, high confidentiality and all-weather work, so near-field measurement is allowed to the standard method for modern antenna measurement and is the reliable method to appraise antenna characteristic. In order to introduce near-field antenna measurement to metrology, the compensated technology for near-field antenna measurement must be studied.The main contents of this paper are as follows: the theory of near-field antenna measurement is analyzed; the main errors in the near-field antenna measurement are analyzed and the compensation methods are provided; the characteristic of open-ended rectangular waveguide is analyzed.In this paper the transformed formula from near-field to far-field is derived, and this process is realized with MATLAB.In order to reduce the effect of probe errors in near-field antenna measurement, the solutions are proposed as follows: On the one hand, theoretical formula of probe-compensated is derived; on the other hand, drop-shaped probe is designed and near-zone gain, far-field patterns, axial ratio, main lobe width, input impedance, voltage standing-wave ratio, electromagnetic field and current distribution of probe are obtained through the computer simulation. Based on simulation result, the gain error of probe can be compensated and a better probe can be designed. In this paper the function of rectangular waveguide in measurement standard is introduced and near-field standard of the microwave metrology is established using standard aperture waveguide.In this paper the effects of scanning truncation error, scanning position error, random amplitude and phase error, and multiple-reflection error in near-field antenna measurement are analyzed; error equations and the uncertainty of measurement are obtained through computer simulation; compensated techniques for reducing the effects of measurement errors in near-field antenna measurement are presented and the formula and arithmetic of phaseless near-field techniques are derived.In a word, the author provides support for introducing near-field antenna measurements to metrology in theory based on this research.